1. Field of the Invention
This invention relates to the pumping of liquids and more particularly to an improved pump for metering a liquid from a container.
2. Description of the Related Art
Metering pumps have been well known in the art for pumping and/or dispensing a specific volume of liquid from a container. There are two basic types of metering pumps namely a single action metering pump and a multiple action metering pump. In a single action metering pump, the liquid is pumped and dispensed in a single action or single stroke of the metering pump. Typically, a volume is filled with a metered volume of liquid from a larger container and then the metered volume of liquid is pumped or discharged from the metered volume for end use.
In a multiple action metering pump, a volume is filled with their metered volume of liquid from a larger container and then the body of liquid is pumped or discharged from the metered volume. Thereafter, the volume is filled again with a metered volume of liquid from a large container and is again pumped or discharged to from the metered volume. The multiple action metering pump has the advantage of being able to discharge greater volumes of metered liquid over the single action metering pump. However, it is more difficult to accurately discharge a metered amount of liquid from a multiple action metering pump than a single action metering pump.
In some cases, a metering pump is used for metering a liquid concentrate for subsequent mixing with a liquid diluent. The accuracy of a metering pump is critical when the liquid concentrate is a highly concentrated liquid. The following United States patents are representative of the attempts of the prior art to provide accurate metering pumps.
U.S. Pat. No. 3,768,704 to Beguin discloses a fluid dispenser comprising a pressurized fluid reservoir connected to one end of which is a flexible flattenable tube the other end of which forms a dispensing outlet. The tube is supported intermediate its ends by an upstream and a downstream support of a frame the section of the tube between these supports being of greater length than the spacing between these supports and being a floating section movable in a space provided by the frame. The floating section can occupy a position in which a major portion thereof extending from the upstream support is inflated by the pressurized fluid and is sealed at its downstream end by a fold in the tube and can be moved from this position by a roller movable in said space in such a way as first to form a fold near the upstream end of the free section sealing a body of fluid in the tube and then to displace the inflated section to open out the folds at the downstream end of the free section to allow the body of fluid to pass from the dispensing outlet of the tube. The roller in the final stages of its dispensing movement stretches the free section of the tube over a convex surface to expel the fluid from the tube. During return movement of the roller the free section of tube is sealed adjacent its downstream end before the tube is again inflated.
U.S. Pat. No. 4,014,318 to Dockum, et al. discloses a circulatory assist device and system for controlling, wholly or partially, the pumping of blood through a blood vessel or vascular prosthesis. The assist device is comprised of an electrically operated plunger, or equivalent, which momentarily occludes the blood vessel to effect pumping. Preferably, a plurality of the assist devices are mounted adjacent each other and are sequentially actuated to sequentially occlude adjacent segments of the associated blood vessel, thereby creating a pumping action. The assist devices are implantable at various locations in the body and may be provided in appropriate size and number to effectively replace heart action. Valves may be utilized to enhance the efficiency or provide pumping with a single assist device.
U.S. Pat. No. 4,165,954 to Amos discloses a linear peristaltic pump. The pump includes a pivotal pump arm and a flexible tube secured thereto to inhibit longitudinal tube movement. A means for applying a force to such arm, such as a spring, is provided to cause the pump arm to pivot. A stop device is disposed in the path of travel of the pump arm so that the pump arm pivotal travel may be terminated as the pump arm comes to rest against such stop device. The flexible tube is disposed adjacent to a surface of the pump arm and is pivotal therewith so that the flexible tube is pinched off between the pump arm surface and the stop device as the pump comes to rest against it. A rotatable roller assembly is provided having at least one roller mounted on a rotatable roller support, the roller intermittently contacting the flexible tube as the roller support is rotated causing a quantity of liquid to be peristaltically moved within the tube. The pump arm may have a concave surface to accommodate the flexible tube and the convex surface of the roller, if desired. The stop device may be adjustable so as to permit adjustment and change of the pivotal travel of the pump arm. The rotatable roller assembly may be caused to intermittently contact the flexible tube through the use of an electric clutch to which the roller assembly is rotatably responsive. The rotatable roller assembly causes the pump arm and flexible tube to pivot in a direction away from the stop device while the means for applying a force causes the pump arm and flexible tube to pivot in a direction towards the stop device.
U.S. Pat. No. 4,722,372 to Hoffman, et al. discloses electrical batteries integrated with a disposable container of flowable material for powering a dispensing apparatus. The disposable container includes a deform able chamber for containing a predetermined quantity of material to be dispensed, and an electrically energized actuating member deforms the chamber for dispensing the flowable material. The dispensing apparatus is actuated by a photocell system which electrically energizes the actuating member in response to the proximity of a user to the dispensing apparatus without the user contacting the apparatus. The photocell system normally is inactive, and is rendered active by a sensor for detecting the proximity of a user to the apparatus.
U.S. Pat. No. 4,967,940 to Blette et al. discloses a method and apparatus for precision control of work fluids in a squeezable tube that has no surge of work material during the shut off closing of the tube which is accomplished by a compensator moving simultaneously and oppositely to the shut off member movement, each of the compensator and the shut off member having different stroke lengths and tube engagable surface areas which effectively keep the internal volume of the tube the same. The method and apparatus are useful standing alone, in coordination with precision positive displacement pumping under computer control which is also presented, and as a part of sequential or simultaneous movement of a valve/pump dispensing head coordinated with a stationary or movable work piece to provide exceedingly fine control dispensing. Suckback between dispensing shots is coordinated with shut off and movements of inlet, outlet and dispensing members to afford operator programmable dispensing with precision and without drip.
U.S. Pat. No. 5,217,355 to Hyman, et al. discloses a linear peristaltic pump for pumping fluid through a resilient tube has a pair of pumping fingers, a pair of pinching fingers, and a strain gauge to monitor pressure inside the tube. The first pumping finger squeezes the tube at a first location, and the second pumping finger squeezes the tube at a second location. Additionally, the first pumping finger is configured and operated to displace approximately twice the fluid volume displaced by the second pumping finger. The first pinching finger occludes the tube upstream to the first pumping finger and the second pinching finger occludes the tube between the first and second pumping fingers. To monitor dimensional changes in the outer diameter of the tube and thereby indicate pressure inside the tube, the strain gauge is mounted on the pump between the second pinching finger and first pumping fingers. Finally, a leaf spring and photoelectric sensor are associated with the first pumping finger to indicate when the finger is in its fully withdrawn position.
U.S. Pat. No. 5,252,044 to Raines, et al. discloses an ambulatory parenteral fluid infusion pump employing a disposable in-line cassette which provides three independent fluid paths between two flexible plastic sheets. The fluid path extends through a pump chamber having a piston plate secured to the flexible sheet at each pumping chamber. The sealed flexible sheets are housed in a rigid housing which provides an aperture through which a catch member formed on the piston plate extends, and having living hinges overlying the inlet and outlet paths for shutting off those paths. An outlet valve is normally closed, and operates in response to buildup of fluid pressure from advancement of the piston plate into the pump chamber to deliver fluid.
U.S. Pat. No. 5,255,822 to Mease, et al. discloses an automatically operated soap dispenser for use in washing the hands of a user is provided in a housing. Enclosed in an intermediate portion of the housing is a horizontally disposed transparent cylindrical chamber having an open front end and an opening in the upper wall thereof. Residing in the upper portion of the housing is a disposable liquid soap container having extending from the bottom thereof a resilient elongated tubular member with a self-sealing nipple valve on the lower end thereof which is positioned in the opening on the upper wall of the cylindrical chamber. A cyclically operated actuating means located in the housing above the cylindrical chamber is controlled to automatically squeeze the tubular member and supply a single quantity of liquid soap through the nipple valve in response to an upturned palm of a hand of the user being inserted into the open front of the cylindrical chamber.
U.S. Pat. No. 5,316,452 to Bogen, et al. discloses a cartridge pump and dispensing assembly for applications where cartridges containing liquid reagents are interchanged often. The cartridge pump comprises a reagent reservoir which directly empties into a metering chamber. A valve is at each end of the metering chamber. The two valves are aligned in the same direction so as to allow unidirectional liquid flow. The metering chamber is made of a compressible material, such as flexible tubing, so that when an external compression is applied to the chamber, the liquid contained therein is forcibly expelled. As the compression is removed, the metering chamber resumes its former shape and draws liquid into the chamber from the reagent reservoir. A dispensing assembly with electromechanical actuators for compression of the metering chamber and a means for sensing the amount of liquid contained within the reagent reservoir are also shown.
U.S. Pat. No. 5,402,913 to Graf discloses a dispenser of a flowable medium, especially a lubricant, with a flexible wall tube forming the pumping chamber which is connected to a container for the flowable medium by a check-valve and feeds a dispensing nozzle. The pumping chamber is deformed by a plunger actuated by a lever in turn displaced by a solenoid whose linearly displaceable rod bears upon the lever.
U.S. Pat. No. 5,593,290 to Greisch, et al. discloses a multiple-chamber pump for dispensing precise volumes of fluids. The pump is especially suited for dispensing volumes in the microliter range. At least three chambers comprising preferably spherical segments are sequentially connected by conduits and are closed by a diaphragm member which is movable into or out of the chambers by application of pressure or vacuum on one side of the diaphragm to draw liquid into the chambers and then to expel the liquid from the chambers, either forward or backward according to an operating sequence. Control means are provided for alternating and sequencing the application of pressure and vacuum such that metered volumes of liquid are pumped from chamber to chamber. Tiny, precisely controlled drops of liquid can be dispensed. A plurality of ganged pumps also can be provided in a single pump body to meter independently a plurality of fluids simultaneously. Advantageously, flows can be joined or split between ganged pumps to provide precise combinations of different fluids. Flows in any of the preferred pump configurations can be dispensed to one or a plurality of dispensing destinations.
U.S. Pat. No. 5,964,583 to Danby discloses a liquid delivery device which controls the flow of liquid from a liquid reservoir having a resilient tubing having a wall with a substantially cylindrical cross-section defining a flow lumen. The flow lumen is in fluid communication with the reservoir. A compression member selectively compresses a lengthwise segment of the cylindrical wall to collapse the flow lumen and releases the lengthwise segment to open the flow lumen. An elastomeric sleeve encloses greater than half an outer diameter of the cylindrical cross-section of the resilient tubing along at least a portion of the lengthwise segment of the cylindrical wall. The elastomeric sleeve biases the lengthwise segment of the resilient tube to restore it to its substantially cylindrical cross-section when the compression member releases the lengthwise segment.
U.S. Pat. No. 6,213,739 to Phallen, et al. discloses a liquid pumping apparatus for pumping liquids, more specifically a linear peristaltic pump apparatus. The apparatus includes a high durometer compressible elastomeric liquid flow tube an infeed valve assembly and an outfeed valve assembly. An extensible and retractable actuator anvil have a round surface which engages the flow tube at all times. An opposed anvil having a round surface engages with the flow tube at all times. The flow tube is held between the anvils in a slightly compressed state when the anvil is retracted. A control assembly causes the movable anvil to be sequentially extended and retracted to cause flow within the flow tube from the infeed valve assembly to the outfeed valve assembly. With this apparatus the lumen of the flow tube to the sides of the anvils is not completely reduced to zero volume during displacement compression whereby gas embolisms do not erupt or explode when discharged.
Although the prior art United States patents have progressed the metering pump art, there is still a need in the art for a very accurate, low cost and reliable metering pump suitable for metering liquid concentrates of a highly concentrated nature.
Therefore, it is an object of the present invention to provide an improved pump for metering a liquid that is capable of accurately metering and discharging a liquid from a container.
Another object of this invention is to provide an improved pump for metering a liquid utilizing a multiple action metering pump for accurately metering and discharging a liquid.
Another object of this invention is to provide an improved pump for metering a liquid that is capable of being programmed for metering and discharging different metered volumes of liquid.
Another object of this invention is to provide an improved pump for metering a liquid that is suitable for metering and discharging a liquid concentrate for mixing with a diluent.
Another object of this invention is to provide an improved pump for metering a liquid that is suitable for metering a liquid concentrate food product containing small quantities of undissolved particles or particulates.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by modifying the invention within the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention, the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.